This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The majority of HIV-1 infections are initiated through sexual contacts that expose the mucosa of the genital and intenstional track to infectious virus. There is, therefore, a need for a vaccine that can generate an immune response that can block this infection. The purpose of this study is to evaluate the efficacy of a HIV vaccine primarily designed to prevent mucosal-route HIV infection by inhibiting HIV entry across the mucosal epithelium.